“Production Logging” is a common, long-established technique for determining the contribution of various producing depth intervals in a hydrocarbon well to the total flow and fluid composition that is observed at surface. Many different sensor types and tool configurations exist to make the measurements that such techniques require.
In a naturally-producing well, where the reservoir pressure is sufficient to cause fluids to flow from the formation into the wellbore, it is relatively simple to lower a logging tool comprising such production logging sensors on wireline or on slickline.
In a well where the reservoir pressure is not sufficient to cause fluids to flow from the formation GF into the wellbore WB, a pumping arrangement PA (often abbreviated as ESP: Electrical Submersible Pump) is required to raise fluids to the surface ST as schematically depicted in FIG. 1. Fluid enters the wellbore below the pumping arrangement. Above the pump, the fluid flows usually in production tubing PT that channels the pumping arrangement output to surface. Clearly, in either case it is necessary to perform the production logging data acquisition below the pumping arrangement, as this is where the fluid is entering the wellbore. However, such a pumping arrangement PA represents a mechanical obstacle to lower a logging tool TL into the wellbore WB.
A first known technique enabling logging below the pumping arrangement is to install a branch in the tubing known as a “Y-tool” YT. The pumping arrangement PA is comprised in one of the branches of the Y-tool YT. By removing a plug in the other branch of the Y-tool YT, the logging tool can be lowered below the pumping arrangement PA. However, this technique requires removing the plug before logging, and replacing it afterwards. Further, with this technique it is necessary to seal around the cable LN while running the production logging acquisition. Furthermore, the pumping arrangement needs to be mechanically bypassed, which restricts the size of both the pumping arrangement and the logging tool.
A second known technique enabling logging below the pumping arrangement is described in document U.S. Pat. No. 6,120,261. This document describes a combined electric motor and submersible pump apparatus intended for installation in line with the well tubing. The apparatus comprises a hollow drive shaft having a downstream end secured to the rotor of the motor and mounted for rotation in axial alignment with the axis of the tubing. The pump impellers are mounted on the upstream end of the hollow shaft. The shaft also has inlet and discharge ports and a check valve mounted on the interior of the drive shaft that is closed when the pump is activated. When the check valve is in the open position, a wire line tool can be passed through the hollow drive shaft to a position below the apparatus. However, this technique requires considerably modifying the structure of the pumping arrangement. Further, it is more expensive than standard pumping arrangements.